Abstract: Mantissa results of floating point operations are truncated to words of 24 bits each by storing the 64 bit mantissa result in a first address location of a random access memory, and storing binary ZEROs in the 48 least significant bit positions of a second address location of the random access memory. The mantissa result is truncated by addressing the high order 24 bits at the first address location and the 48 binary ZEROs at the second address location.

Abstract: Digital data is recorded on the surface of a magnetic media such as a disk or diskette in the form of magnetic flux transitions identifying clock and data information in a modified frequency modulation (MFM) mode. A read head senses the flux transitions which are in turn converted to digital signals. A counter in the adapter starts to count when the adapter receives a digital signal. The count is transferred to a register and the counter presets when the adapter receives the next digital signal. The count is indicative of the time between the successive digital signals and should be representative of multiples of an integer. The count signals stored in the register address a read only memory whose output signals preset the counter to a value to compensate for the difference between the expected time and the actual time between the successive digital signals thereby reducing the read error rate.

Abstract: If the firmware calls for an operand rounding operation, apparatus in the Scientific Instruction Processor (SIP) tests the bit to the right of the low order bit of the normalized operand to determine if a rounding cycle is required. If the operand requires a normalization cycle or a mantissa overflow correction cycle, the rounding operation is performed in those cycles.

Abstract: A Scientific Instruction Processor (SIP) uses a Programmable Read Only Memory (PROM) to control the output of a two stage shifter. The shifter performs the necessary mantissa shift operations of shift right, shift left, shift right around, as well as inserting certain constant information into the system. Control signals and shift signals applied to the input address terminals of the PROM select the PROM output signals which enable the selected mantissa hexadecimal digits which output the shifter. This forces hexadecimal digits from the enabled positions and hexadecimal ZERO digits in those positions not enabled.

Abstract: In a microprogrammed data processing system in which the boundaries of the operands or data strings identified by the descriptors are not constrained to coincide with boundaries of the units of addressable memory space, i.e., words, the time required to retrieve, execute and store operands of a three descriptor instruction, wherein two descriptors define the memory address of the initial operands and the third descriptor defines the memory address of the resulting operand, can be reduced by prefetching the two words which include the boundaries of the operand (data string) identified by the third descriptor. After execution of the instruction, the boundary words of the resulting operand (data string) can have the rewrite data, that is the data of the boundary words which are not part of the resulting operand, and should therefore be retained and inserted in appropriate positions of the appropriate boundary word by a retrieval of the boundary words which do not interrupt the normal data processing sequence.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which, in response to a microword indicating that the result of the decimal numeric calculation is a short operand, that is, a predetermined number of words or less, and in accordance with an instruction descriptor, generates a count of the number of words of the resultant operand the decimal unit will transfer to memory.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which is conditioned by the instruction descriptors in advance of receiving the operands to align the decimal digits of the operand words as the words are received by the apparatus from memory.The descriptor information for each operand includes the scale factor, the position of the sign, the position of the most significant character within the word, whether it is a floating point or scaled operand, the number of bits in each decimal character, either 4 or 9 bits, and the length of the operand.The apparatus is conditioned by the descriptor information to align the two operands for processing.

Abstract: Apparatus in a Cathode Ray Tube (CRT) display allows the sharing of the system bus between the microprocessor (CPU) and Direct Memory Access (DMA) devices without degrading the CPU performance by splitting the system bus cycle into an address phase and a data phase.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased by apparatus which counts the number of leading zero digits of an operand on the cycle in which the operand word is processed through the decimal unit and sends that count to the execution unit in response to a predetermined microword.The apparatus counts the number of leading zero digits by first storing in a register the number of words the decimal unit will not send for processing as determined by an instruction descriptor. As the operand is received by the decimal unit, most significant word first, the number of leading zero digits in the operand is added to the register on the same cycle the operand word is processed through the decimal unit, thereby generating a count of the number of zero digits in the operand that the decimal unit will send for processing. This leading zero digit count is available to the firmware in response to a microword command.

Abstract: In a microprogrammed data processing system the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which indicates to the microprogram the characteristics of the operand being processed. This enables the proper microprogram subroutine; that is, if the operand is a floating point or a scaled number, has 4-bit decimal digits or 9-bit decimal digits, has an overpunched leading sign or trailing sign, has an adjusted length less than or equal to 63 decimal digits, whether the operand is a long or short operand, and whether the resulting operand is equal to zero or has an overflow.

Abstract: Information to be written in the form of magnetic flux reversals on the surface of a disk or diskette is applied in serial fashion to a first shift registor. The parallel outputs of the shift register address a PROM. The PROM output is applied to a second shift register in the form of clock and data bits to be written on the disk or diskette magnetic surface. Control signals applied to the PROM address terminals select the mode, FM or MFM, the address mark or if precompensation is required.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which receives a long operand, greater than a predetermined number of words, which is the result of the calculation, assembles the resultant operand in accordance with an instruction descriptor, and transfers the resultant operand to memory.

Abstract: A cathode ray tube display terminal system includes a central processor subsystem and a number of certain peripheral subsystems all of which are coupled in common to a system bus. Apparatus in the central processor subsystem receives interrupt request signals from certain of the peripheral subsystems and on a predetermined priority basis modifies an address generated by the central processor subsystem in dependence upon which of the requesting certain peripheral subsystems has the highest priority. The modified address, called a vectored address points to a firmware subroutine stored in a memory subsystem which is also coupled to the system bus and which processes the interrupt from the highest priority cetain peripheral subsystem. Other peripheral subsystems coupled to the system bus generate a single interrupt signal which is also applied to the apparatus in the central processor system.

Abstract: A microprocessor controlled cathode ray tube display system has a plurality of peripheral devices all connected in common to a system bus. Apparatus in each peripheral device activates a single interrupt signal. A single acknowledge response signal to all the devices enables the interrupting device to place its address signals on the system bus thereby initiating a firmware routine for making the interrupting device operative with the system.

Abstract: In a microprogrammed data processing system, the throughput of the system is increased by apparatus which counts the number of effective digits in an operand which is the result of a decimal numeric instruction being processed by the system. The apparatus receives operand words the operand's least significant word first, in response to a predetermined microword.The apparatus includes a first register which stores a count of one less than the number of words received; an adder which increments the output of the first register if the word received has a decimal zero in the high order position of the word; and a second register which stores the output of the adder in a word count portion and the number of leading zeros in a digit count portion of the second register. The second register is loaded on the same cycle the word is processed providing the word does not contain all decimal zeros.

Abstract: A multiprogramming/multiprocessing computer system for executing a plurality of processes sharing common information in the form of records, pages or messages, employing an apparatus for avoiding an interference between two processes seeking access to elements of common information. The system operates to store in a first memory utilization data in table form identifying the processes which have accessed each individual element of common information. A second memory stores a matrix of precedence data representing the relative order in which processes must access the common information in accordance with a predetermined set of access rules. When a first process enters a request to access an element of common information, the system identifies from the utilization table any other process which, according to the access rules, must be given precedence to the common information over the first process.

Abstract: In a microprogrammed data processing system the throughput of the system is increased during the processing of decimal numeric instructions by apparatus which strips zone bits, sign, exponent and non-operand characters from the operand when the operand is received from memory and appends the zone bits, sign, exponent and non-operand characters to the resultant operand when stored into memory. The control signals for stripping and appending information is enabled by shifter logical elements.

Abstract: A word oriented data processing system includes a plurality of system units all connected in common to a system bus. Included are a central processor unit (CPU), a memory system and a high speed buffer or cache system. The cache system is also coupled to the CPU. The cache includes an address directory and a data store with each address location of directory addressing its respective word in data store. The CPU requests a word of cache by sending a memory request to cache which includes a memory address location. If the requested word is stored in the data store, then it is sent to the CPU. If the word is not stored in cache, the cache requests the word of memory. When the cache receives the word from memory, the word is sent to the CPU and also stored in the data store.

Abstract: A first in-first out buffer memory coupled to a system bus receives all information transferred over the bus. Logic associated with the buffer memory tests if the information received is intended to update main memory or is in response to a cache request. The information is written into cache if the main memory address location is stored in a cache directory. The information received in response to a cache request is stored in a cache data buffer. Other information is discarded.

Abstract: A data processing system includes a central processor subsystem, a main memory subsystem and a cache subsystem, all coupled in common to a system bus. During the overall system initialization process, apparatus in the cache subsystem effects the transfer of information from the main memory subsystem to the cache subsystem to load all address locations of the cache subsystem. The transfer of information from the main memory subsystem to the cache subsystem starts from the lowest order address locations in main memory and continues from successive address locations until the cache subsystem is fully loaded. This assures that the cache subsystem contains valid information during normal data processing.